Re: [PATCH v2 1/4] hyperv: Introduce new hypercall interfaces used by Hyper-V guest IOMMU

[Yu Zhang <zhangyu1@linux.microsoft.com>]

On Thu, Jul 09, 2026 at 07:06:19PM +0000, Michael Kelley wrote:
> From: Yu Zhang <zhangyu1@linux.microsoft.com> Sent: Thursday, July 2, 2026 9:05 AM
> > 
> > From: Wei Liu <wei.liu@kernel.org>
> > 
> > Hyper-V guest IOMMU is a para-virtualized IOMMU based on hypercalls.
> > Introduce the hypercalls used by the child partition to interact with
> > this facility.
> > 
> > These hypercalls fall into below categories:
> > - Detection and capability: HVCALL_GET_IOMMU_CAPABILITIES is used to
> >   detect the existence and capabilities of the guest IOMMU.
> > 
> > - Device management: HVCALL_GET_LOGICAL_DEVICE_PROPERTY is used to
> >   check whether an endpoint device is managed by the guest IOMMU.
> > 
> > - Domain management: A set of hypercalls is provided to handle the
> >   creation, configuration, and deletion of guest domains, as well as
> >   the attachment/detachment of endpoint devices to/from those domains.
> > 
> > - IOTLB flushing: HVCALL_FLUSH_DEVICE_DOMAIN is used to ask Hyper-V
> >   for a domain-selective IOTLB flush (which in its handler may flush
> >   the device TLB as well).
> > 
> > Signed-off-by: Wei Liu <wei.liu@kernel.org>
> > Co-developed-by: Easwar Hariharan <easwar.hariharan@linux.microsoft.com>
> > Signed-off-by: Easwar Hariharan <easwar.hariharan@linux.microsoft.com>
> > Co-developed-by: Yu Zhang <zhangyu1@linux.microsoft.com>
> > Signed-off-by: Yu Zhang <zhangyu1@linux.microsoft.com>
> > ---
> >  include/hyperv/hvgdk_mini.h |   8 +++
> >  include/hyperv/hvhdk_mini.h | 124 ++++++++++++++++++++++++++++++++++++
> >  2 files changed, 132 insertions(+)
> > 
> > diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
> > index 6a4e8b9d570f..5bdbb44da112 100644
> > --- a/include/hyperv/hvgdk_mini.h
> > +++ b/include/hyperv/hvgdk_mini.h
> > @@ -486,10 +486,16 @@ union hv_vp_assist_msr_contents {	 /*
> > HV_REGISTER_VP_ASSIST_PAGE */
> >  #define HVCALL_GET_VP_INDEX_FROM_APIC_ID		0x009a
> >  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE	0x00af
> >  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST	0x00b0
> > +#define HVCALL_CREATE_DEVICE_DOMAIN			0x00b1
> > +#define HVCALL_ATTACH_DEVICE_DOMAIN			0x00b2
> >  #define HVCALL_SIGNAL_EVENT_DIRECT			0x00c0
> >  #define HVCALL_POST_MESSAGE_DIRECT			0x00c1
> >  #define HVCALL_DISPATCH_VP				0x00c2
> > +#define HVCALL_DETACH_DEVICE_DOMAIN			0x00c4
> > +#define HVCALL_DELETE_DEVICE_DOMAIN			0x00c5
> >  #define HVCALL_GET_GPA_PAGES_ACCESS_STATES		0x00c9
> > +#define HVCALL_CONFIGURE_DEVICE_DOMAIN			0x00ce
> > +#define HVCALL_FLUSH_DEVICE_DOMAIN			0x00d0
> >  #define HVCALL_ACQUIRE_SPARSE_SPA_PAGE_HOST_ACCESS	0x00d7
> >  #define HVCALL_RELEASE_SPARSE_SPA_PAGE_HOST_ACCESS	0x00d8
> >  #define HVCALL_MODIFY_SPARSE_GPA_PAGE_HOST_VISIBILITY	0x00db
> > @@ -502,6 +508,8 @@ union hv_vp_assist_msr_contents {	 /*
> > HV_REGISTER_VP_ASSIST_PAGE */
> >  #define HVCALL_MMIO_READ				0x0106
> >  #define HVCALL_MMIO_WRITE				0x0107
> >  #define HVCALL_DISABLE_HYP_EX                           0x010f
> > +#define HVCALL_GET_IOMMU_CAPABILITIES			0x0125
> > +#define HVCALL_GET_LOGICAL_DEVICE_PROPERTY		0x0127
> >  #define HVCALL_MAP_STATS_PAGE2				0x0131
> > 
> >  /* HV_HYPERCALL_INPUT */
> > diff --git a/include/hyperv/hvhdk_mini.h b/include/hyperv/hvhdk_mini.h
> > index b4cb2fa26e9b..493608e791b4 100644
> > --- a/include/hyperv/hvhdk_mini.h
> > +++ b/include/hyperv/hvhdk_mini.h
> > @@ -547,4 +547,128 @@ union hv_device_id {		/* HV_DEVICE_ID */
> >  	} acpi;
> >  } __packed;
> > 
> > +/* Device domain types */
> > +#define HV_DEVICE_DOMAIN_TYPE_S1	1 /* Stage 1 domain */
> > +
> > +/* ID for default domain and NULL domain */
> > +#define HV_DEVICE_DOMAIN_ID_DEFAULT 0
> > +#define HV_DEVICE_DOMAIN_ID_NULL    0xFFFFFFFFULL
> > +
> > +union hv_device_domain_id {
> > +	u64 as_uint64;
> > +	struct {
> > +		u32 type: 4;
> > +		u32 reserved: 28;
> > +		u32 id;
> > +	} __packed;
> > +};
> > +
> > +struct hv_input_device_domain {
> > +	u64 partition_id;
> > +	union hv_input_vtl owner_vtl;
> > +	u8 padding[7];
> > +	union hv_device_domain_id domain_id;
> > +} __packed;
> > +
> > +union hv_create_device_domain_flags {
> > +	u32 as_uint32;
> > +	struct {
> > +		u32 forward_progress_required: 1;
> > +		u32 inherit_owning_vtl: 1;
> > +		u32 reserved: 30;
> > +	} __packed;
> > +};
> > +
> > +struct hv_input_create_device_domain {
> > +	struct hv_input_device_domain device_domain;
> > +	union hv_create_device_domain_flags create_device_domain_flags;
> > +} __packed;
> > +
> > +struct hv_input_delete_device_domain {
> > +	struct hv_input_device_domain device_domain;
> > +} __packed;
> > +
> > +struct hv_input_attach_device_domain {
> > +	struct hv_input_device_domain device_domain;
> > +	union hv_device_id device_id;
> > +} __packed;
> > +
> > +struct hv_input_detach_device_domain {
> > +	u64 partition_id;
> > +	union hv_device_id device_id;
> > +} __packed;
> > +
> > +struct hv_device_domain_settings {
> > +	struct {
> > +		/*
> > +		 * Enable translations. If not enabled, all transaction bypass
> > +		 * S1 translations.
> > +		 */
> > +		u64 translation_enabled: 1;
> > +		u64 blocked: 1;
> > +		/*
> > +		 * First stage address translation paging mode:
> > +		 * 0: 4-level paging (default)
> > +		 * 1: 5-level paging
> > +		 */
> > +		u64 first_stage_paging_mode: 1;
> > +		u64 reserved: 61;
> > +	} flags;
> > +
> > +	/* Address of translation table */
> > +	u64 page_table_root;
> > +} __packed;
> > +
> > +struct hv_input_configure_device_domain {
> > +	struct hv_input_device_domain device_domain;
> > +	struct hv_device_domain_settings settings;
> > +} __packed;
> > +
> > +struct hv_input_get_iommu_capabilities {
> > +	u64 partition_id;
> > +	u64 reserved;
> > +} __packed;
> > +
> > +struct hv_output_get_iommu_capabilities {
> > +	u32 size;
> > +	u16 reserved;
> > +	u8  max_iova_width;
> > +	u8  max_pasid_width;
> > +
> > +#define HV_IOMMU_CAP_PRESENT (1ULL << 0)
> > +#define HV_IOMMU_CAP_S2 (1ULL << 1)
> > +#define HV_IOMMU_CAP_S1 (1ULL << 2)
> > +#define HV_IOMMU_CAP_S1_5LVL (1ULL << 3)
> > +#define HV_IOMMU_CAP_PASID (1ULL << 4)
> > +#define HV_IOMMU_CAP_ATS (1ULL << 5)
> > +#define HV_IOMMU_CAP_PRI (1ULL << 6)
> 
> hvgdk_mini.h mostly uses the Linux BIT() and BIT_ULL()
> macros instead of explicit shifts. But this is hvhdk_mini.h.
> Does it need to play by a different set of rules for
> compatibility with the original Windows files? I think
> the Linux BIT* macros are preferable if possible. 
> 

I'm not aware of any compatibility requirement. And since it
does not change the real definition, I guess we should use
BIT*.

> > +
> > +	u64 iommu_cap;
> > +	u64 pgsize_bitmap;
> > +} __packed;
> > +
> > +enum hv_logical_device_property_code {
> > +	HV_LOGICAL_DEVICE_PROPERTY_PVIOMMU = 10,
> > +};
> > +
> > +struct hv_input_get_logical_device_property {
> > +	u64 partition_id;
> > +	u64 logical_device_id;
> > +	/* Takes values from enum hv_logical_device_property_code. */
> > +	u32 code;
> > +	u32 reserved;
> > +} __packed;
> > +
> > +struct hv_output_get_logical_device_property {
> > +#define HV_DEVICE_IOMMU_ENABLED (1ULL << 0)
> 
> Same here about BIT_ULL().
> 

Will fix. Thanks!

B.R.
Yu

> > +	u64 device_iommu;
> > +	u64 reserved;
> > +} __packed;
> > +
> > +struct hv_input_flush_device_domain {
> > +	struct hv_input_device_domain device_domain;
> > +	u32 flags;
> > +	u32 reserved;
> > +} __packed;
> > +
> >  #endif /* _HV_HVHDK_MINI_H */
> > --
> > 2.52.0
> > 
>